Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

889
FXUS63 KLOT 140137
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
837 PM CDT Sat Jun 13 2026

.KEY MESSAGES...

- Isolated to widely scattered thunderstorms possible later this
  evening, though the threat of severe weather has decreased.

- Dangerous swimming conditions at NW Indiana Lake Michigan
  beaches Sunday.

- Cooler temperatures early next week.

- Shower and thunderstorm chances return Tuesday and Wednesday.
  The possibility exists for another severe weather event on
  Wednesday.

&&

.UPDATE...
Issued at 837 PM CDT Sat Jun 13 2026

Convection had struggled earlier this afternoon, remaining
limited in coverage. This was likely due to a lack of low-level
convergent focus, extensive cloud cover from upstream convection
and some impediment to stronger deep-moisture advection from
MCS cold pool from lower MO Valley region to our southwest.
Latest surface analysis indicates a cold front entering far
northwest and western IL however, which should result in an
increase in low-level forcing and shower/thunderstorm coverage
heading into the late evening and early overnight hours. DVN 00Z
RAOB indicates an impressive 3200 J/kg MUCAPE and 30 kts of
effective shear, which would continue to support some storm
organization and a severe threat (wind/hail) for any cells that
can persist for a while. So far, updrafts have struggled to
maintain west of and over our western cwa, though we`ll continue
to monitor those trends. Any severe threat should end from west
to east with the passage of the surface cold front later this
evening around Rockford and around/after midnight for Chicago
and our southeastern counties. Locally heavy rainfall will also
need to be monitored with relatively slow cell motions and
especially if any training occurs. Post-frontal showers also
look to persist through daybreak or so, before finally ending
early Sunday morning.

With the much smaller footprint of convective activity from
this afternoon into early/mid evening had lowered pops quite a
bit. Otherwise, going forecast remains generally on track
overnight through Sunday - with breezy, cooler and less humid
conditions.

Ratzer

&&

.DISCUSSION...
Issued at 324 PM CDT Sat Jun 13 2026

Recently, a few isolated showers and storms developed across
parts of LaSalle eastward into southern Kendall and Grundy
counties, but have since decayed. Otherwise, we continue to
monitor the threat for more substantial scattered showers and
storms (some of which could be strong/severe) with a cold
frontal passage this evening. Forecast guidance continues to
support an uptick in scattered shower and thunderstorm
development late this afternoon and evening in advance of this
front. This appears plausible given that a mid-level impulse
currently shifting eastward across IA will be overspreading the
frontal zone as it moves into northern IL after 5 pm this
evening. Additionally, low-level moisture return continues in
advance of the front, and is noted by surface dewpoints already
increasing into the upper 60s to near 70 in parts of northern
IL.

Considering the environment in which these storms are, and will
be, developing features deep-layer bulk shear in excess 35 kt,
there remains a threat for some storms to become strong to
severe into this evening. Accordingly, the SPC continues to have
our area in a level 1 of 5 severe threat through this evening.
While certainly not looking to be an outbreak of severe storms
like the area experienced on Thursday, a few of the strongest
storms could produce localized damaging wind gusts in excess of
60 mph and possibly a few instances of hail. The main threat of
storms will end from northwest to southeast through the mid to
late evening hours.

A few lingering scattered showers may linger in the wake of the
cold frontal boundary for a period late tonight into early
Sunday morning as the main mid-level impulse dives into the
area. However, this activity is expected to quickly exit the
region early Sunday, setting up a precipitation free day for the
area. Temperatures will be much cooler for Sunday in the wake
of this cold frontal passage, as breezy northwest winds (gusting
up to 30 mph) usher in a cooler airmass. Accordingly, expect
high temperatures generally in the low to mid 70s Sunday
afternoon. The only real weather concern for Sunday is at Lake
Michigan Beaches across northwestern Indiana, where the onshore
breezy winds build waves up to 3 to 5 feet, setting the stage
for a high swim risk. With this in mind, we have opted to hoist
a Beach Hazard statement for our Lake IN and Porter county
beaches on Sunday.

Another tranquil weather day is anticipated on Monday, though
with a bit warmer temperatures. Thereafter, upper troughing,
anchored by a Hudson bay area low, will support an enhanced belt
of mid and upper-level northwesterly upper-level flow across
the central CONUS through mid to late week. This should result
in a return to a more active weather pattern again (return of
showers and thunderstorms) for the middle of next week, which
may drive another significant impulse into the lower Great Lakes
region on Wednesday. Wednesday is thus another day to watch
closely for our next potential notable severe weather threat.

KJB

&&

.AVIATION /00Z TAFS THROUGH 06Z MONDAY/...
Issued at 640 PM CDT Sat Jun 13 2026

Aviation forecast concerns for the 00Z TAFs:

- Extent of any TSRA coverage expected to be lower than previous
  forecast thinking, and later this evening.

- Lingering scattered SHRA may persist from after midnight
  through around daybreak. Patchy MVFR vis/ceilings possible.

- Surface winds turn northwest behind a cold front late tonight,
  and become breezy Sunday with gusts 20-25 kt.

Early evening surface analysis depicts a cold front moving
slowly east-southeast across central/southwest WI and far
eastern IA. While airmass ahead of this front had destabilized
to some degree (with a few convective SHRA/TS attempts since
this afternoon), extensive cloud cover and remnant cold pool
from earlier convective complex across the lower MO/OH Valley
regions has suppressed destabilization and deeper moisture
return to some extent. While isolated to widely scattered
SHRA/TS can`t completely be ruled out early this evening, it
appears better forcing for higher convective coverage will be
focused along/just ahead of the approaching cold front. In
addition, a smaller footprint of convection appears likely, and
thus have backed off a few hours of PROB30 mention after 01Z at
RFD and 03Z for the Chicago terminals.

The cold front is expected to move through RFD around 04Z and
ORD/MDW around 06Z, with a wind shift from WSW to NW. A mid-
level disturbance lagging the front should produce a period of
at least scattered showers behind the front overnight through
around daybreak Sunday. Patchy MVFR vis/ceilings are possible
in/near these showers. After daybreak and with increased diurnal
mixing, northwest winds will become breezy with gusts 20-25 kt
likely, with a BKN VFR stratocu deck lingering at least part of
the day.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Beach Hazards Statement from 7 AM CDT Sunday through Sunday
     evening for INZ001-INZ002.

LM...None.

&&

$$

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